The Epidemiology and Biostatistics Research Core includes ten NIEHS Center investigators whose primary affiliations are in the Departments of Environmental Medicine or Obstetrics-Gynecology. Members are all principal investigators on peer-reviewed grants except for one new junior member who is a co-investigator on grants in two Cores in the Center. During the past five years several previous members have retired (Pasternack), died (Dubin) or left (Taioli, Bernstein, Lee, Skovron, Hu, and Rousch) the institution. Additional exclusions were because of the stringent membership criteria of peer-reviewed funded research. The focus of the Epidemiology and Biostatistics Core is to develop new understanding of the impact of environmental factors upon human health and the joint effects of xenobiotic and endogenous factors. Identification of environmental determinants or co-factors in disease can lead to environmental interventions that will reduce the disease burden for exposed populations. An additional premise is that a range of susceptibilities to toxic exposures exists in the population, so that identification of the most susceptible, whether due to genetic predisposition, age, ethnic variation or other co-acting exposures will help ensure that protection of vulnerable members of the society. To address these issues, the epidemiology portfolio includes studies that characterize the risk from a number of environmental agents that seek to identify subsets of persons at increased risk of disease by using biological markers of exposure or susceptibility to disease. The types of studies underway include collaborations with other core members within the Core and with other research cores. The themes of their research program includes effects of radiation exposure, environmental exposures (Drs. Shore, Kato, Toniolo, Friedman-Jimenez, Koenig, Zeleniuch-Jacquotte, and Xue), studies of occupational respiratory disease (Drs. Rom, Friedman-Jimenez, and de la Hoz), hormonally mediated diseases (Drs. Toniolo, Zeleniuch-Jacquotte, Koenig, Kato, and Kim), dietary factors and chemoprevention of cancer (Drs. Kato, Toniolo, Koenig, Zeleniuch-Jacquotte, and others), hereditary cancer and gene-environment interactions (Drs. Shore, Xue, and Toniolo), applications of statistical methods to environmental health studies (Drs. Kim and Xue), and risk assessment (Drs. Shore and Friedman-Jimenez).